Punishers of malefactors earn trust points from others

By Bill Hathaway

February 24, 2016

Why do many people go out of their way to punish those who have done wrong to others — even when the punishers themselves have not been personally harmed?

One answer is that punishers earn “trust points” that benefit them in the future, according to a new study by Yale University researchers, which suggests that it can actually be adaptive to feel moral outrage that drives you to punish transgressions.

“The gains in reputational benefits can outweigh the costs of intervening to punish a wrongdoer,” said Jillian J. Jordan, Ph.D. student in the Department of Psychology and lead author of the study published Feb. 25 in the journal Nature.

Psychologists and evolutionary biologists have long asked why people are motivated to sacrifice time, resources, or even personal safety to punish those who harm others. People protest injustice, become whistleblowers, boycott products from companies that do social harm, and cut ties with unethical friends or colleagues. A prevailing theory is that while individual punishers may pay a price, groups and society as a whole benefit from such “third-party punishment.”

Jordan and senior author David Rand, associate professor of psychology and economics, created a mathematical model demonstrating how individuals too can benefit from seemingly selfless acts of punishment by gaining a reputation for being trustworthy. To test the theory, they ran experiments in which one subject was asked whether she would give up money to punish someone who had acted reprehensively. A second subject observing the experiment then decided whether she would entrust money to the first subject. The researchers found that observers were more likely to entrust their money to those who had punished malefactors.

“And they were right to be more trusting — punishers really were more trustworthy, and returned more money,” Jordan said.

Interestingly, note the scientists, when experimenters also gave subjects the opportunity to appear trustworthy by directly giving money to another individual, rates of punishment went down — and people stopped caring about punishment when deciding who to trust. Instead, they focused on trusting those who had generously shared with others.

“Although you may not consciously realize it, our results suggest that you punish to show others that you are trustworthy when you do not have the chance to help more directly,” Rand said.

The authors say this type of punishment plays a similar social role as the peacock’s tail in evolution. Although the peacock’s tail makes it difficult for the bird to move and avoid predators, it is also an advertisement of its health and fitness and desirability as a mate. Likewise, say the researchers, while our sense of moral outrage may motivate us to take costly actions, it serves to signal that we can be trusted to do the right thing.

Moshe Hoffman of Harvard and Paul Bloom of Yale are co-authors of the study.